Internal-combustion engine



G. F. DILLIG.

INTERNAL COMBUSTION ENGINE.

APPLICATION FILED IAN. I3, 1921.

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GEORGE E. DILLIG, OF PITTSBURGH, PENNSYLVANIA."

INTERNAJLFCOMBUSTION ENGINE.

Specification of Letters Patent.

Patented Aug. 9, 1921.

Applications filed January 13, 1931. Serial no. 486,910.

To all whom it may concern:

Be it known that I, GEORGE F. DILLIG, a citizen of the United States,.and residing in the city of Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented or discovered new, useful, and Improved Tnternal Combustion Engines, of which the following is a specification.

My invention consists of certain new and useful improvements in internal combustion engines, having reference to thetype of engine wherein the air alone is compressed while the fuel is injected into the firing cylinder at approximately the moment of maximum compression, and also to especially a balanced, two stroke super-charging engine.

The objects which I have in view are,inte1' a-Zia, as follows:

To provide simple and practical means for charging the firing cylinder with an initialair volume at or exceeding atmospheric pressure, so as to minimize the decrease in horse power in air craft engines at high altitudes due to diminished atmospheric pressure at such altitudes.

To produce a light and compact engine wherein all the rotating and translation forces, and also the torque reactions of a pair of crank shafts rotating in opposite directions are in substantial balance.

To provide a multiple cylinder or unit engine, operating on the two stroke principle having means for thoroughly exhausting and scavenging the products of the exploded charges and means for admittin to the firing cylinders the supply of air tor the next charge at a substantial lag after the opening and closing of the exhaust ports, thus conserving the compressed air and protecting the air admission mechanism from the heat and pressure of the explosions.

To provide a suitable design of internal combustion engine having no valves exposed to the action of the firing charge, simple to fabricate, cpmposed of relatively few parts, capable of being quickly assembled or taken down, and easy to maintain at maximum efficiency.

These objects are attained by my new balanced, supercharging internal combustion engine, hereinafter described.

Generally speaking, my improved engine is characterized by a plurality of parallel units, each composed of a main cylinder structure provided with a central firing cylinder, and a compressor cylinder at both ends of the firing cylinder and of larger diameter than the latter. in each unit are a pair of differential pistons working in opposite directions, their smaller diameters moving in the firing cylinder, while their larger diameters move in the compressor cylinders. Two crank shafts are provided, rotating in opposite directions and synchronized in their movement to which said pistons are connected. The air charge for each cylinder is first given an initial compression in the compressor cylinders of the unit-firing next before the first mentioned cylinder. The inward movements. of the pistons complete the compression of the air charge in the firing cylinder, and at approximately the point of maximum compression of the charge, the fuel, such as crude oil, is injected into the firing cylinder and exploded either by the heat of compression or by any other convenient means.

Ports, which are uncovered by the pistons on their outward stroke, are provided for the admission of the air charge into the fir-.

ing cylinder and the escape and scavenging of the products of the explosion of the charge from said cylinder, the opening and closing of the air admission ports being arranged to lag somewhat behind the opening and closing of the exhaust ports, whereby the air valve mechanism is protected from the heat and pressure of explosion and the scavenging of the products of combustion from the firing cylinder and the refilling of the cylinder with air are rendered thorough and complete.

An improved rotary valve mechanism for supplying the air charge to the several units is provided, and the same is effectually protected from the firing heat and pressure, so that its efiicient operation is not impaired.

Means are provided whereby at high altitudes, at which the lessened atmospheric pressure tends to reduce the horse power of the engine, the volume of air in the compressors is increased by discharging into the compressors air under compression in the crank cases, thus enabling the compressors to supply the firing cylinders with an initial charge at a pressure exceeding atmospheric pressure. Many other novel features of construction and arrangement of parts will appear from the following description.

In the accompanying drawings, which are merely intended to illustrate a practical embodiment of the principles of myinvention and not to limit the scope of the same to the construction shown, Figure 1 is a plan view, partially in horizontal section of a multiple supercharging engine embodying my invention, two of the piston rods being omitted to better show parts; Fig. 2 is a vertical, longitudinal section taken along the line II- II in Fig. 1; Fig. 3 is a vertical, cross section taken along the line III-1H in Fig. 2; Fig. 4 is a similar view taken along the line TV-IVin Fig. 1; Figs. 5, 6, and 7 are sections taken, respectivel along the lines VV, VI-Vl[ and VI VII in Fig. 1;

work in the compressor cylinders.

Fig. 8 is an enlarged detail sectional view on enlarged scale showing the fuel injector and the method of inserting it into the firing cylinder, and Fig. 9 is also a broken detail in section on enlarged scale, showing the method of mounting the firing cylinders and their water jacket tubes in the engine.

The following is a detailed description of the drawings.

The construction shown in the drawings illustrates a multiple engine provided w1th three arallel units or main cylinder struc tures X, A and At, a pair of crank shafts B and B rotating in opposite directions and synchronized, as by the lay shaft C, and a pair of differential pistons D working in opposite directions in each cylinder member and connected to said crank shafts. I

Each cylinder unit is formed of a central firing cylinder 1 and two end compressor cylinders 2 of larger diameter. The smaller diameters of the pistons work in the central firing cylinders while their larger diameters 3 represents the piston rods which connect the pistons to the proper crank shafts.

The crank cases E and E are conveniently formed of two castings, preferably aluminum, an outer casting 4 and an inner casting 5, integral with which latter are cast the compressor cylinders 2.

One end of said crank cases is closed by a circular plate 6 bolted in place and provided with an axial bearing 7 for the end of the crank shaft. The other end of the crank cases is provided with a similar plate 8 provided with an axial bearing 9 for the crank shaft. Each crank throw rotates in a separate crank chamber formed in the crank case by the ribbed diaphragm 10.

A beveled gear 11 is mounted. on the end of each crank shaft outside of the bearings 9, which ears intermesh with similar gears 12 on t e ends of the lay shaft C which is journaled adjacent to its ends in the bearlugs 13 carried by the gear boxes 14 mounted on the ends of the crank cases. Thus the crank shafts are synchronizedas they rotate in opposite directions.

The firing cylinders 1 are formed of tubes, preferably of steel or cast iron whose ends are inserted in the contracted outer ends of the compressor cylinders 2. 15 represents exterior annular shoulders on said tubes adjacent to their ends which abut and bear. against the adjacent end portions of the castings 5 to limit the entrance of the ends of the tubes 1 into said castings.

Near one of its ends, adjacent to the crank case E in the drawings, each of the firing cylinders 1 is provided with a semi-annular series of elongated ports 16 about its upper semi-circumference, which ports communicate with an air port 17 extending up through the casting 5 and communicating with the bottom interior of a cylindrical valve casing F. This casing may also be an aluminum casting bolted or otherwise mounted on top of the adjacent crank case casting 5.

Adjacent to its other end each of said firing cylinders 1 is provided with a circumferential series of elongated ports 18, of greater capacity than the ports 16, communicating with an annular passage 19 in the casting 5 surrounding said firing cylinder. Ribs 19* integral with the casting 5 cross said passage between the ports 18 to support the cylinder tube and to tie the casting together. The passage 19 communicates through an open port 20 with an exhaust manifold 21 which may be of suitable metal and secured to the underside ofthe adjacent crank case, as shown.

22 is a metal tube surrounding the central portion of each firing cylinder to form a water jacket for the same, and having its ends supported by the annular lips 23 on the ends of the castin's- 5. The water space within said tube 22 is connected by ports not shown with the water spaces 24 in the castings 5 and with the water supply tube 25. Any convenient means for maintaining a flow of water through the water passages ma be used.

he crank ca'se castings, the firing cylinder tubes and the water jacket tubes are clamped rigidly together. by means of long tension bolts 26, extending from end to end of the engine and passing through the tubes 27 cast integral with the crank case castings. Nuts 28 are screwed onto the end of said bolts to tighten the parts together.

I have shown eight of said bolts, but the number may be increased if deemed necessary.

The inner end of each of the compressor cylinders 2 of the crank case E are connected by an open port 29 with a passage 30 in the wall of the valve casing F running circumferentially of said casing around the same to a point near the bottom of the casing casting. The other end of each of said passages 30 is connected by a tube or passage 31 with an open port 32 at the inner end of one of the compressor cylinders 2 of the crank case E A port 33 adjacent to the tube 31 connects each of the passages 30 with the bore ofthe valve casing F.

G is the rotary valve, also preferably an aluminum casting, seated in the casing F. 34 are ball bearings interposed between the ends of said valve and the casing to reduce friction. One end of the casing F is closed by the screw cap 35 while the other end of the valve protrudes from the valve casing and is provided with a gear 36 which meshes with a gear 37 keyed on the lay shaft 0. Said gears are inclosed in a gear box 38 mounted on the casing F and through which the shaft C extends.

The intermediate portion of said valve G is provided with an axial cylindrical chamber 39 surrounded by a concentric annular chamher 40. 41 represents ports extending from the central chamber 39 to the exterior of said valve. There is one of said ports 41 for each firing cylinder and the center of said ports are spaced 120 degrees apart around the circumference of said valve, each port 41 being adapted to register in turn with the corresponding port 17, as the valve rotates counterclockwise.

Said ports 41 are so located that when one of said ports, say that of unit A, is asso ciated with the corresponding port 17 as shown in Fig. 2, the correspondlng port 41 associated with unit A will be in the position shown in Fig. 5, while the port 41 associated with the unit A will be in the position shown in Fig. 6, it being assumed that the valve is rotating counterclockwise and the units are fired in the order A, A and A the port 41 of a given unit'being located 120 degrees ahead of the corresponding port 41 of the unit next previously fired. Between the passages 30 in the casing F, there are provided partially circumferential passages 42in the wall of said casing, communicating with atmosphere at their tops by means of the open ports 43. Said passages are in communication with the bore of the casing F by means of a plurality of equally spaced ports 44, and 45 represents an annular series of' ports in the outer wall of the valve G concentric with each of the passages 42 in the casing. Thus the annular chamber 40 in the valve is in substantially constant communication with atmosphere.

Opposite each of the ports 41 the outer wall of the valve G is provided with a large port 46.

Thus, when the pistons are moving outwardly in a unit, as in the case of unit A Fi 2, the ports 33 and 46 register, as shown in T ig. 6, so that air is drawn into. the compressor cylinders 2 of said unit. When the pistons are moving inwardly, as in the case of unit A Fig. 2, the ports 33 and 46 are out of registration, as in Fig. 5, but the port 41 is in registration with the port 33, so that the air beln'g compressed in the compressor cylinders, asshown in cylinders 2 of unit A is forced in to the central chamber 39 of the valve, and is forced out through the proper port 41 through the corresponding port 17 into the firing cylinder 1 of the unit A, as shown in Fig. 2, when the ports 16 of said firing cylinder are uncovered.

Thus, as the pistons in unitA complete their outstroke and the air ports 16' are uncovered, the pistons of unit A force acharge of air at greater than atmospheric pressure through the rotary valve G into the firing I cylinder of unit A. Meanwhile, the charge of air previously introduced into the firing cylinder of unit A. by the pistons of unit A is being compressed to explode the fuel charge which will be injected into said firing cylinder at approximately the moment of maximum pressure. Meanwhile, the pistons of unit A are drawing in air from atmosphere through the rotary valve into their compressor cylinders 2. Thus, on each outstroke of its pistons air is sucked into the compressed cylinders of a unit and toward the end of the instroke of the pistons, while the air charge is being compressed in the firing chamber of said unit, air is also forced from said compressor cylinders into the firin cylinder of the unit next to be fired.

he crank throws of a crank shaft are spaced 120 degrees apart, and the crank throws of the crank shaft B connected with the pistons controlling the exhaust portsof the several firing cylinders, are given a slight lead over the corresponding cranks of the crank shaft connected with the pistons controlling the air inlet ports of such firin ig. 2. Thus, the e haust ports are opened and closed by the pistons in advance of the opening and 0105- 105 ing of the corresponding inlet ports. By this lag of the air ports, I am enabled to partially vent the products of combustion after an explosion of a charge from the fir ing cylinder before the air ports are opened. 110 This protects the rotary valve mechanism from the impulse and heat of the explosion of the charge, assists in thoroughly scaveng ing the products'of combustion from the firing cylinder and assures the complete filling 115 of the firing cylinder with a fresh charge of air under pressure.

The liquid fuel, such as crude or other oil, is introduced through an injector, such as the tube H, into the firing cylinders of 120 each unit at approximately the moment of maximum compression. In the drawings I have shown such as injector tube H extending into the firing cylinder 1 between the dotted lines in Fig. 2 which are intended to 125 represent the terminations of the instrokes of the pistons- A convenient method of inserting the tube H is as follows. 47 is a port in the wall of cylinder tube 1 and 48 is an internally threaded collar welded or 130 cast to the outer wall of the tube 1 with its bore registering with said port and its outer end bearing against the inner wall of the tube 22. 49 is a bushing adapted to be screwed into the said collar and provided with a flanged head which bears against the wall of the tube 22 and clamps the same rigidly to the tube 1. The injector tube H may be inserted into the firing cylinder through said bushing, as shown. Any form of mechanism for the delivery of the roper quantity of fuel through said tube into the firing cylinder at the proper intervals ma be provided.

Iii aeroplane practice, such high altitudes are frequently attained that the diminished atmospheric pressure results in lessened horse power developed by the engine. To overcome this tendency and to maintain the approximately highest power under such circumstances, I provide means whereby, when necessary, the initial air charge in the firing cylinders at about the closing of the exhaust ports will be at a pressure greater than atmospheric pressure.

This I accomplish by either single or two stages initial compression. In the case of single stage compression the displacement of the differential pistons in the compressor cylinders is substantially of much larger capacity than the piston displacement in the firing cylinder. But in the case of two stage compression a further advantage is taken to obtain this result by producing the first stage compression in the crank case compartments and discharging the contents into the differential compressor cylinders.

Thus, the compressor cylinders 2 are prolonged outwardly into the interiors of the crank cases and provided near their outer ends with an annular series of air ports 50 which are uncovered as the pistons approach the ends of their outstroke. The crank cases are also provided with suitable air valves such as the valves 51 adapted to be opened inwardly by the suction of the pistons on their instroke and normally held closed by the helical springs 52. A valve is provided for each crank throw compartment.

It is evident that with the spring pressure properly adjusted, the inward movement of the pistons will cause the valves 51 to open and admit air into the crank cases, while the outward movement of said pistons will close said valves and cause the air trapped in the crank cases to be com ressed and to enter the compressor cy inders through the ports 50. During the inward movement of the pistons, this air is further compressed together with the air previously sucked in through the rotary valve and the Y combined volume toward the end of the instroke of the pistons discharged through the rotary valve into the firing chamber of the unit next in order of firing, thus supplying the firing cylinders with an initial charge at a pressure greater than atmospheric pressure. By means of levers 53, the aviator may hold said valves 51 open until the altitude requires the use of the crank cases as auxiliary compressors, as above described.

It is evident from the foregoing that my improved supercharging balanced engine is of very light and compact construction. That it works at the highest etficiency in a wide range of atmospheric pressure. The forces set up by the movement of its parts and by propeller torque are balanced. It is of inexpensive yet durable construction. It

may be quickly assembled and taken down,

and has a minimum number of parts. The arrangement of a pair of crank shafts rotating in opposite directions and accurately synchronized, especially adapts my engine for use in air craft having two propellers, capable of great speed and large lifting capacity.

The weights of the opposed moving parts in a given unit are equal and their velocities at a given instant are practically the same. Therefore the inertia forces are balanced.

In the embodiment of my invention illustrated in the drawings, I show, for the sake of illustration, an engine comprising a. group of cylinder units, the air compressed 1n the compressor cylinder of one unit being charged into the firing chamber of another unit of the group; but it will be understood that'any number of groups of units, with any convenient number-of units in each group, can be provided in one engine.

What I desire to claim is 1. In a balanced two stroke internal combustion engine, the combination of a group of units each comprising a pair of alined compressor cylinders and a firing cylinder of less diameter interposed between the same, a pair of differential pistons working in opposite directions in each of said units, a palr of crank shafts at opposite ends of said units coupled to the adjacent pistons, and means whereby the air compressed in the compressor cylinders of each unit is discharged into the firing cylinder of the unit next in order of firing.

2. In a balanced two stroke internal combustion engine, the combination of a group of units each comprising a pair of alined compressor cylinders and a firing cylinder of less diameter interposed between the same, a pair of differential pistons working in opposite directions in each of said units, a pair of crank shafts at opposite ends of said units coupled to the adjacent pistons, and means whereby air is drawn into each pair of compressor cylinders during the outstroke of their respective pistons and on the merges ihstroke said air is compressed and discharged into the firing cylinder of the unit next in order of firing.

3. In a balanced two stroke internal combustion engine, the combination of a group of units each comprising a pair of alined compressor cylinders and a firing cylinder of less diameter interposed between the same, a pair of difierential pistons Working in opposite directions in each of said units a pair of crank shafts at opposite ends of said units coupled to the adjacent pistons, and a rotary valve operated from said crank shafts adapted to admit air in turn into each pair of compressor cylinders during the outstroke of their respective pistons and to deliver the air compressed by the instroke of said pistons to the firing chamber of the unit next in order of firing.

a. in a balanced two stroke internal combustion engine wherein the fuel is separately introduced into the firing cylinders the combination of a group of units each comprising a pair of alined compressor cylinders and a and on the instroke said air is compressed firing cylinder of less diameter interposed between the same, a pair of difi'erential pistons working in opposite directions in each of said units, a pair of crank shafts at opposite ends of said units coupled to adjacent pistons, means whereby the air compressed in the compressor cylinders of each unit is discharged into the firing cylinder of the unit next in order of firing, and means for injecting fuel into each firing cylinder at approximately the moment of maximum compression of the air in said firing cylinder.

5. In a balanced two stroke internal combustion engine wherein the fuel is separately introduced into the firing cylinders, the combination of a group of units each comprising a pair of alined compressor cylinders and a firing cylinder of less diameter interposed between the same, a pair of differential pistons working in opposite directions in each of said units, apair of crank shafts at o posite ends of said units coupled to the a jacent pistons, means whereby air is drawn into each pair of compressor cylinders during' the outstroke of their respective pistons and discharged into the firing cylinder of the unit next'in order of firing, and means for injecting fuel into each firin cylinder at approximately the moment 0 maximum aompression of the air in said firing cylin- 6. In a balanced two stroke internal combustion engine wherein the fuel is separately introduced into-the firing cylinders, the combination of a group of units each comprising a pair of alined compressor cylinders and a firing cylinder of less diameter interposed between the same, a pair of differential pistons working in opposite directions in each of said units, a pair of crank shafts at opposite ends of said units coupled to the adj acent pistons, a rotary valve operated from said crank shafts adapted to admit air in turninto each pair of compressor cylinders during the outstroke of their respective pistons and to deliver the air compressed by the instroke of said pistons to the firing chamber of the unit next in order of firing and means for injecting fuel into each firing cylinder at approximately the moment of maximum compression of the air in said firi cylinder.

7. n a balanced supercharging two stroke internal combustion engine, the combination of a group of parallel units, each comprising a pair of spaced apart and alined compressor cylinders and a firing cylinder of smaller diameter interposed between the same, a pair of differential pistons working in opposite directions in each unit, a pair of parallel crank shafts one mounted at each endof said units and'coupled to the adjacent pistons, a lay shaft j ournaled parallel with said units and geared at its ends to said crank shafts to synchronize the latter, and a rotary valve driven by said lay shaft and adapted to admit fiuid' in turn to each pair of compressor cylinders during the outstroke of their pistons and to discharge the fluid compressed during the instroke of said pistons into the firing cylinder of the unit next in order of firing.

8, In a balanced supercharging two stroke internal combustion engine, the combination of a group of parallel units, each comprisin opposite directions in each unit, a pair of parallel crank shafts one mounted at each end of'said units and coupled to the adjacent pistons, a lay shaft journaled parallel with said units and geared at its ends to said crank shafts to synchronize the latter, a rotary valve driven by said lay shaft and adapted to admit air in turn to each pair of compressor cylinders duri' the outstroke of their pistons and todischarge the air compressed during the instroke of said pistons into the firing cylinder-of the unit next in order of firing, and means for injecting a fuel charge into each firin cylinder at approximately the moment 0% maximum compression.

9. In a balanced supercharging two stroke internal combustion engine, the combination of a group of parallel units, each comprising a pair of spaced apart and alined compressor cylinders, and a firing cylinder of smaller diameter interposed between the same, a pair I crank shaftsone mounted at each end of said units and connected with the adjacent pistons, a valve casing connected with each firing cylinder by a port, passagesconnecting each pair of compressor cylinders in unison with said valve casing, and a rotary valve mounted in said casing and driven in unison by said crank shafts whereby fluid is admitted to each pair of compressor cylinders during the outstroke of their pistons and the fluid compressed by the instroke of said pistons is discharged into the firing cylinder of the unit next in order of firing.

10. In a balanced supercharging two stroke internal combustion engine, the combination of a group of parallel units each comprising a pair of spaced apart and alined compressor cylinders and a firing cylinder of smaller diameter interposed between the same, a pair of differential pistons working in opposlte directions in each unit, a pair of parallel crank shafts one mounted at each end of said units and connected with the adjacent pistons, a valve casing connected with each firing cylinder by a port, passages connecting each pair of compressor cylinders in unison with said valve casing, a rotary valve mounted in said casing and driven in unison by said crank shafts whereby air is admitted to each pair of compressor cylinders during the outstroke of their pistons and the air compressed by the instroke of said pistons is discharged into the firing cylinder of the unit next in order of firing, and means for injecting a fuel charge into each firing cylinder at approximately the moment of maximum compression.

11. In a balanced two stroke internal combustion engine, the combination of a group of units each comprising a pair of alined compressor cylinders and a firing cylinder of less diameter interposed between the same, a pair of differential pistons working in opposite directions in each of said units, an inclosed crank case divided into crank throw compartments, at each end of said units, a crank shaft journaled in each of said crank cases and coupled to the adjacent pistons, means for introducing air into said crank throw compartments during the inward strokes of the corresponding pistons, means for admitting the air trapped in said compartments into the corresponding compressor cylinders during the outward strokes of their pistons and means for discharging the air compressed in said compressor cylinders during the inward stroke of their pistons into the firing cylinder of the unit next in order of firing.

12. In a balanced two stroke internal combustion engine wherein the fuel is separately introduced into the firing cylinders, the combination of a group of units each. comprising a pair of alined compressor cylinders and a firing cylinder of less diameter interposed between the same, a pair of differential pistons working in opposite directions in each of said units, an inclosed crank case, divided into crank throw compartments, at each end of said units, a crank shaft journaled in each of said crank cases and coupled to the adjacent pistons, means for introducing air into said crank throw compartments during the inward strokes of the corresponding pis tons, means for admitting the an trapped in said compartments into the corresponding compressor cylinders during the outstrokes of their pistons, means for discharging the air compressed in said compressor cylinders during the inward strokes of their pistons into the firing cylinder of the unit next in order of firing, and means for injecting fuel in each firing cylinder at approximately the moment of maximum compression of air in said firing cylinder.

13. In a balanced supercharging two stroke internal combustion engine, the com bination of a group of units each comprising a pair of spaced apart and alined compressor cylinders and a firing cylinder of smaller diameter interposed between the same, each of said firing cylinders being provided with an inlet port adjacent to one of its ends and an outlet port adjacent to its other end, a pair of differential pistons working in opposite directions in each unit and controlling .said ports, means whereby the fluid compressed in the compressor cylinders of each unit is discharged into the firing cylinder of the unit next in orderof firing, and a pair of crank shafts one at each end of said units and coupled to the adjacent pistons, the throws of the crank shaft coupled to the pistons controlling the exhaust ports being slightly in advance in the direction of rotation, of the throws of the crank shaft coupled to the pistons controlling the inlet ports, whereby the opening and closing of the inlet ports lag behind the opening and closing of the exhaust ports, for the purposes set forth.

14. In a balanced supercharging internal combustion engine, the combination of a pair 'of parallel crank cases, a crank shaft journaled in each crank case, said crank shafts being synchronized and rotating in opposite directions, a group of cylinder units interposed between said crank cases each comprising a compressor cylinderadjaoent to each crank case and a firing cylinder of less diameter interposed between said compressor cylinders and alined therewith, a pair of differential pistons for each unit working in opposite directions in said cylinders and coupled to adjacent crank shafts and means whereby the fluid compressed in thecompressor cylinders of each unit is discharged into the firing cylinder of the unit next in order of firing, the weights of the opposed rotating and. reciprocating parts being equal, and

their velocities at a given instant substantially the same, whereby the inertia forces are balanced.

g 15. In a balanced superchargingtwo stroke internal combustion engine, the combination of a pair of parallel crank cases, cylinder units interposed between said crank cases, each unit comprising a pair of spaced apart and' alined compressor cylinders and a firing cylinder of smaller dlameter interposed between the same, a pair of differential pistons working in opposite directions in each of said units, means whereby the fluid compressed in the compressor cylinder of each unit is discharged into the firing cylinder of the unit next in order of firing, and a crank shaft in each ofsaid crank cases, said crank shaft rotating in opposite directions and being'coupled to the adjacent pistons,

the weights of the opposing rotating and reciprocating parts being equal and their velocities at a given instant being substantially the same, whereby the rotating and rectilinear forces and reactions are balanced.

16. In a balanced supercharging two stroke internal combustion engine, the combination of a pair of parallel crank cases,

cylinder units interposed between said crank cases, each unit comprising a pair of spaced apart and alined compressor cylinders and a firing cylinder of smaller diameter interposed between the same, a pair of differential pistons workin in opposite directions in each of said unlts, means whereby the fluid compressed in the compressor cylinder of each unit is discharged into the firing cylinder of the unit next in order of firing, a crank shaft in each crank case, said crank shafts rotating in opposite directions and being coupled to the adjacent pistons, a lay shaft coupling said crank shafts together so that they are synchronized to rotate together in opposite directions the weights of the opposing rotating and reciprocating parts being equal and their velocities at a given instant being substantially the same, whereby the rotating and rectilinear forces and reactions are balanced;

Signed at Pittsburgh, Pa, this 12th day of January, 1921.

GEORGE E. DILLIG. 

